Microstructure Analysis of Modified Asphalt Mixtures under Freeze-Thaw Cycles Based on CT Scanning Technology

The modifiers NTC (nano-TiO2/CaCO3) and BF (basalt fiber) were adopted to modify a base matrix asphalt mixture. The base matrix asphalt mixture and three kinds of modified asphalt mixture under F-T (freeze-thaw) cycles were scanned by computed tomography. The air voids and morphological changes of asphalt mixture were summarized by image processing technology, and the development process of F-T damage to asphalt mixture was explained from a micro-view. The porosity of NTC-modified asphalt mixture changed little, and the void distribution between base matrix asphalt mixture and NTC-BF (nano-TiO2/CaCO3 and basalt fiber) composite modified asphalt mixture was more uniform. The macro-pores in the asphalt mixture under 15 F-T cycles began to connect gradually, and the pore characteristics also changed. The number and shape of the pores changed under 15 F-T cycles. According to the state characteristics, the change amplitude of the pore characteristics of matrix asphalt mixture and NTC-BF composite modified asphalt mixture were the most stable under F-T cycles.